Liquid crystal display device including driving circuit and method of fabricating the same

ABSTRACT

A method of fabricating an array substrate structure for a liquid crystal display device includes defining a display area and a non-display area on a substrate, the display area having a pixel TFT portion and a pixel electrode area, and the non-display area having an n-type driving TFT portion and a p-type driving TFT portion; forming a first gate electrode in the display area, a second and a third gate electrodes and a first capacitor electrode in the non-display area; an amorphous silicon layer on the substrate; crystallizing the amorphous silicon layer to a polycrystalline silicon layer and doping specific portions of the polycrystalline silicon layer with plurality of impurity concentrations; and forming a first semiconductor layer in the display area, a second and a third semiconductor layers and a second capacitor electrode in the non-display area.

This application is a Divisional of prior application Ser. No.10/998,844, filed Nov. 30, 2004, now U.S. Pat. No. 7,410,817 whichclaims the benefit of Korean Patent Application No. 2004-023445 filed onApr. 6, 2004, and which is hereby incorporated by reference in itsentirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly, to a display device including a driving circuitpolycrystalline silicon driving circuit and a method of fabricating thesame.

2. Discussion of the Related Art

As the information age progresses, flat panel display (FPD) deviceshaving high portability and low power consumption is becoming the trendof recent research and development. Among various types of FPD devices,liquid crystal display (LCD) devices are commonly used as monitors fornotebook and desktop computers because of their ability to displayhigh-resolution images, wide ranges of different colors, and movingimages.

In general, the LCD device includes a color filter substrate and anarray substrate separated from each other by having a liquid crystallayer interposed there between, wherein the color filter substrate andthe array substrate include a common electrode and a pixel electrode,respectively. When a voltage is supplied to the common electrode and thepixel electrode, an electric field is generated that changes theorientation of liquid crystal molecules of the liquid crystal layer dueto optical anisotropy within the liquid crystal layer. Consequently,light transmittance characteristics of the liquid crystal layer ismodulated and images are displayed by the LCD device.

Active matrix type display devices are commonly used because of theirsuperiority in displaying moving images. Active matrix-type displaydevices include pixel regions disposed in a matrix form where a thinfilm transistor (TFT) is formed in the pixel region as a switchingelement. While forming the TFT, hydrogenated amorphous silicon (a-Si:H)is selected to be deposited over a large area of substrate. Hydrogenatedamorphous silicon yields higher productivity while easily fabricated onthe large area of the substrate. In addition, the hydrogenated amorphoussilicon (a-Si:H) is deposited at a temperature less than about 350° C.,a glass substrate of low cost can be used. Accordingly, the hydrogenatedamorphous silicon is used mainly in the TFT, which is referred to as anamorphous silicon thin film transistor (a-Si TFT).

However, since the hydrogenated amorphous silicon has a disorderedatomic arrangement, weak silicon-silicon (Si—Si) bonds and danglingbonds exist in the hydrogenated amorphous silicon. These types of bondsbecome metastable when light or an electric field is applied to thehydrogenated amorphous silicon. As a result, this metastability makesthe TFT unstable. Electrical characteristics of the hydrogenatedamorphous silicon are especially degraded due to light irradiation.Furthermore, a TFT using the hydrogenated amorphous silicon is difficultto be implemented in a driving circuit due to degraded electriccharacteristics such as a low field effect mobility between about 0.1cm²/Vsec to about 1.0 cm²/Vsec, and poor reliability.

In the related art TFT, the substrate including the a-Si TFT isconnected to a printed circuit board (PCB) using a tape carrier package(TCP) that has a driving integrated circuit (IC). The driving IC and itspackaging increase the LCD device production cost. Additionally, as theresolution of a liquid crystal display panel for an LCD deviceincreases, a pad pitch between gate pads or between data pads of thea-Si TFT substrate becomes smaller. Thus, bonding of the TCP and thea-Si TFT substrate becomes harder.

To solve these problems, a polycrystalline silicon thin film transistor(p-Si TFT) is suggested. Due to a higher field effect mobility of a p-SiTFT as compared to an a-Si TFT, fabrication of a driving circuit and aswitching element can be achieved simultaneously. Accordingly, theproduction cost is reduced and the TCP is removed. Moreover, p-Si TFTcan be used as a switching element of a high-resolution panel to benefitfrom the high field effect mobility of the polycrystalline silicon.Furthermore, a p-Si TFT has a lower photo current than an a-Si TFT,thereby preventing the display device from the substantial degradationof display quality due to the exposure to light.

FIG. 1 is a schematic view showing a liquid crystal display deviceaccording to the related art where a switching element and a drivingcircuit are formed on a single substrate. In FIG. 1, a driving circuitportion 5 and a display area 3 are defined on a single substrate 1. Thedisplay area 3 is disposed at a central portion of the substrate 1,while the driving area 5 is disposed at left and top portions of thedisplay area 3. The driving circuit portion 5 includes a gate drivingcircuit 5 a and a data driving circuit 5 b. The display area 3 includesa plurality of gate lines 7 connected to the gate driving circuit 5 aand a plurality of data lines 9 connected to the data driving circuit 5b. The gate line 7 and the data line 9 intersect each other to define apixel region “P”. A pixel electrode 10 is formed in the pixel region“P.” A thin film transistor (TFT) “T” formed as a switching element isconnected to the pixel electrode 10. The gate driving circuit 5 asupplies a scan signal to the TFT “T” from the gate line 7 and the datadriving circuit 5 b supplies a data signal to the pixel electrode 10from the data line 9.

The gate driving circuit 5 a and the data driving circuit 5 b areconnected to an input terminal 12 to receive external signals.Accordingly, the gate driving circuit 5 a and the data driving circuit 5b process the externals signals from the input terminal 12 to generatethe scan signal and the data signal. To generate the scan signal and thedata signal, the gate driving circuit 5 a and the data driving circuit 5b include a plurality of TFTs forming complementarymetal-oxide-semiconductor (CMOS) logic. For example, an inverterincluding negative (n)-type and positive (p)-type TFTs may be formed inthe gate driving circuit 5 a and the data driving circuit 5 b.

FIGS. 2A to 2F are schematic cross-sectional views showing a process offabricating a thin film transistor in a display area of a liquid crystaldisplay device according to the related art. FIGS. 3A to 3F areschematic cross-sectional views showing a process of fabricating n-typeand a p-type thin film transistors in a driving area of a liquid crystaldisplay device according to the related art.

In FIGS. 2A and 3A, a buffer layer 25 is formed on a substrate 20 and anamorphous silicon layer is formed on the buffer layer 25. The amorphoussilicon layer is crystallized to a polycrystalline silicon layer by alaser annealing method. The amorphous silicon layer may bedehydrogenated before crystallizing to a polycrystalline silicon layer.The polycrystalline silicon layer is patterned through a first maskprocess to form a first semiconductor layer 30 in a pixel TFT portion“I,” a second semiconductor layers 35 in an n-type driving TFT portion“II” and a third semiconductor layer 40 in a p-type driving TFT portion“III.”

In FIGS. 2B and 3B, a gate insulating layer 45 of silicon oxide (SiO₂)is formed on the semiconductor layers 30, 35 and 40. After depositing ametallic material on the gate insulating layer 45, first, second andthird gate electrodes 50, 55 and 60 are formed on the gate insulatinglayer 45 through a second mask process. Then, the semiconductor layers30, 35 and 40 are doped with low concentration n-type (n−) impuritiesusing the gate electrodes 50, 55 and 60 as doping masks. Accordingly, aportion of the first semiconductor layer 30 directly underneath thefirst gate electrode 50 is not doped with n− impurities, while the otherportion of the first semiconductor layer 30 is doped with n− impurities.Similarly, the second and third semiconductor layers 35 and 40 arepartially doped with n− impurities. As a result, the semiconductorlayers 30, 35 and 40 are divided into undoped regions 30 a, 35 a and 40a and n− doped regions 30 b, 35 b and 40 b. The undoped regions 30 a, 35a and 40 a are used as an active region of a TFT.

In FIGS. 2C and 3C, first, second and third n+ photoresist (PR) patterns61, 62 and 63 are formed through a third mask process. The first andsecond n+ PR patterns 61 and 62 cover the first and second gateelectrodes 50 and 55, respectively. In addition, the first n+ PR pattern61 covers a predetermined portion of the first semiconductor layer 30adjacent to the first gate electrode 50 and the second n+ PR pattern 62covers a predetermined portion of the second semiconductor layer 35adjacent to the second gate electrode 55. The third n+ PR pattern 63completely covers the third semiconductor layer 40 including the thirdgate electrode 60. Next, the first, second and third semiconductorlayers 30, 35 and 40 are doped with high concentration n-type impurities(n+) using the first, second and third n+ PR patterns 61, 62 and 63 asdoping masks. Accordingly, the predetermined portions of the first andsecond semiconductor layers 30 and 35 are not doped with n+ impurities,while the exposed portions of the first and second semiconductor layers30 and 35 are doped with n+ impurities. In addition, the thirdsemiconductor layer 40 is not doped with n+ impurities. As a result, theexposed portions of the first and second semiconductor layers 30 and 35become n+ doped regions 30 c and 35 c, which are used as an ohmiccontact regions of n-type, and the predetermined portions of the firstand second semiconductor layers 30 and 35 that remain n− doped regions30 b and 35 b are used as a lightly doped drain (LDD) region. Therefore,the active regions 30 a and 35 a, the LDD regions 30 b and 35 b, and then-type ohmic contact regions 30 c and 35 c are defined by doping with n−impurities and n+ impurities. After doping with n+ impurities, thefirst, second and third n+ PR patterns 61, 62 and 63 are removed.

In FIGS. 2D and 3D, the first and second p+ PR patterns 65 and 66 areformed through a fourth mask process. The first and second p+ PRpatterns 65 and 66 completely cover the first and second semiconductorlayers 30 and 35, respectively. The third semiconductor layer 40 isexposed, since no p+ PR pattern is provided in the portion “III”. Next,the semiconductor layers 30, 35 and 40 are doped with high concentrationp-type (p+) impurities using the first and second p+ PR patterns 65 and66 and the third gate electrode 60 as doping masks. Accordingly, thefirst and second semiconductor layers 30 and 35 are not doped with p+impurities. In addition, a portion of the third semiconductor layer 40directly underneath the third gate electrode 60 is not doped with p+impurities, while the other portion of the third semiconductor layer 40is doped with p+ impurities. Since the p-type impurities has aconcentration higher than the n-type impurities in the exposed portionof third semiconductor layer 40, the p-type impurities compensate then-type impurities. Accordingly, the exposed portion of the thirdsemiconductor layer 40 becomes p+ doped region 40 b which is used as anohmic contact region of p-type. Therefore, the active regions 40 a andthe p-type ohmic contact region 40 b are defined by doping with p+impurities. After doping with p+ impurities, the first and second p+ PRpatterns 65 and 66 are removed.

In FIGS. 2E and 3E, an interlayer insulating layer 70 of an inorganicinsulating material such as silicon nitride (SiN_(x)) and silicon oxide(SiO₂) is formed on the gate electrodes 50, 55 and 60 through a fifthmask process. The interlayer insulating layer 70 has semiconductorcontact holes 73 a, 73 b, 75 a, 75 b, 77 a and 77 b defined through thegate insulating layer 45 to expose the ohmic contact regions 30 c, 35 cand 40 c. First source and drain electrodes 80 a and 80 b, second sourceand drain electrodes 83 a and 83 b, and third source and drainelectrodes 87 a and 87 b are formed on the interlayer insulating layer70 through a sixth mask process. The source and drain electrodes 80 a,80 b, 83 a, 83 b, 87 a and 87 b have a double layer structure formed ofmolybdenum (Mo) and aluminum-neodymium (AlNd), and are connected to theohmic contact regions 30 c, 35 c and 40 c within the semiconductorcontact holes 73 a, 73 b, 75 a, 75 b, 77 a and 77 b.

In FIGS. 2F and 3F, a passivation layer 90 of silicon nitride (SiN_(x))is formed on the source and drain electrodes 80 a, 80 b, 83 a, 83 b, 87a and 87 b through a seventh mask process. The passivation layer 90 maybe hydrogenated and has a drain contact hole 95 exposing the first drainelectrode 80 b. Next, a pixel electrode 97 of indium-tin-oxide (ITO) isformed on the passivation layer 90 through an eighth mask process. Thepixel electrode 97 is connected to the first drain electrode 80 b withinthe drain contact hole 95.

As mentioned above, the array substrate for an LCD device according tothe related art is fabricated through a eight-mask process. Since therelated art mask process includes steps of coating PR, exposing PR, anddeveloping PR, increase in production cost and fabrication time as wellas a reduced production yield results from an increased number of masks.In addition, reliability of a thin film transistor is reducedaccordingly.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a liquid crystaldisplay device and a method of fabricating the same that substantiallyobviates one or more of the problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide a liquid crystaldisplay device having a bottom gate structure and a method offabricating the same through a reduced number of mask processes.

Another object of the present invention is to provide an array substratefor a liquid crystal display device and a method of fabricating the samewhere production yield is improved and fabrication cost is reduced basedon a five-mask process.

Another object of the present invention is to provide a thin filmtransistor for a liquid crystal display device and a method offabricating the same where source and drain electrodes are formed afterforming a passivation layer on a semiconductor layer of polycrystallinesilicon to protect a channel.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. These andother advantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a method offabricating an array substrate structure for a liquid crystal displaydevice includes sequentially disposing a transparent conductive materiallayer and a metallic material layer on a substrate defining a displayarea and a non-display area, the display area having a pixel TFT portionand a pixel electrode area, and the non-display area having an n-typedriving TFT portion and a p-type driving TFT portion; forming a firstgate electrode in the pixel TFT portion, a second gate electrode in then-type driving TFT portion, a third gate electrode in the p-type drivingTFT portion, a gate line in the display area, a pixel electrode in thepixel electrode area, and a first capacitor electrode connected to thepixel electrode through a first mask process; sequentially disposing agate insulating layer and an amorphous silicon layer on the first gateelectrode, the second gate electrode, the third gate electrode, the gateline, the pixel electrode and the first capacitor electrode; doping theamorphous silicon layer in the p-type driving TFT portion with highconcentration p-type impurities (p+) through a second mask process todefine a first active region and a first ohmic contact region; dopingthe amorphous silicon layer in the pixel TFT portion and the n-typedriving TFT portion with high concentration n-type impurities (n+) andlow concentration n-type impurities (n−) through a third mask process todefine second and third active regions, second and third ohmic contactregions, first and second lightly doped drain (LDD) regions and astorage capacitor area; disposing a passivation layer on the amorphoussilicon layer; forming a first semiconductor layer in the pixel TFTportion, a second semiconductor layer in the n-type driving TFT portion,a third semiconductor layer in the p-type driving TFT portion, a secondcapacitor electrode in the storage capacitor area through a fourth maskprocess; forming a passivation pattern on the first, second and thirdsemiconductor layers and the second capacitor electrode through thefourth mask process, wherein side portions of each of the first, secondand third semiconductor layers are exposed; and forming first source anddrain electrodes, second source and drain electrodes, third source anddrain electrodes and a data line through a fifth mask process, portionsof the first source and drain electrodes contacting the side portions ofthe first semiconductor layer, portions of the second source and drainelectrodes contacting the side portions of the second semiconductorlayer, portions of the third source and drain electrodes contacting theside portions of the third semiconductor layer, and the data lineconnected to the first source electrode.

In another aspect, a method of fabricating an array substrate structurefor a liquid crystal display device includes sequentially disposing atransparent conductive material layer and a metallic material layer on asubstrate defining a display area and a non-display area, the displayarea having a pixel TFT portion and a pixel electrode area, and thenon-display area having a driving TFT portion; forming a first gateelectrode in the pixel TFT portion and a second gate electrode in thedriving TFT portion, a gate line in the display area, a pixel electrodein the pixel electrode area through a first mask process, wherein afirst capacitor electrode connects to the pixel electrode; sequentiallydisposing a gate insulating layer and an amorphous silicon layer on thefirst, second gate electrodes, the gate line, the pixel electrode, andthe first capacitor electrode; doping the amorphous silicon layer withimpurities through a second mask process to define a first activeregion, a first ohmic contact region, and storage capacitor area in thepixel TFT portion, and a second active region and a second ohmic contactregion in the driving TFT portion; disposing a passivation layer on thepolycrystalline silicon layer; forming a first semiconductor layer inthe pixel TFT portion, a second semiconductor layer in the driving TFTportion, a second capacitor electrode in the storage capacitor area, anda passivation pattern on the first and second semiconductor layers andthe second capacitor electrode through a third mask process, sideportions of each of the first and second semiconductor layers areexposed using the passivation pattern; and forming first source anddrain electrodes, second source and drain electrodes, and a data linethrough a fourth mask process, the first source and drain electrodescontacting the side portions of the first semiconductor layer, thesecond source and drain electrodes contacting the side portions of thesecond semiconductor layer, and the data line connected to the firstsource electrode.

In another aspect, an array substrate structure for a liquid crystaldisplay device includes first, second and third gate electrodes on asubstrate having a display area and a non-display area, the display areahaving a pixel TFT portion and a pixel electrode area, and thenon-display area having an n-type driving TFT portion and a p-typedriving TFT portion, the first gate electrode disposed in the pixel TFTportion, the second gate electrode disposed in the n-type driving TFTportion, the third gate electrode disposed in the p-type driving TFTportion; a gate line in the display area on the substrate; a pixelelectrode in the pixel electrode area on the substrate; a gateinsulating layer on the first, second, and third gate electrodes, thegate line, and the pixel electrode; first, second and thirdsemiconductor layers of polycrystalline silicon on the gate insulatinglayer, the first semiconductor layer disposed in the pixel TFT portion,the second semiconductor layer disposed in the n-type driving TFTportion, and the third semiconductor layer disposed in the p-typedriving TFT portion; a passivation pattern on the first, second andthird semiconductor layers, the passivation pattern exposing sideportions of each of the first, second and third semiconductor layers;first source and drain electrodes, second source and drain electrodes,and third source and drain electrodes on the substrate, the first sourceand drain electrodes contacting the side portions of the firstsemiconductor layer, the second source and drain electrodes contactingthe side portions of the second semiconductor layer, the third sourceand drain electrodes contacting the side portions of the thirdsemiconductor layer; and a data line crossing the gate line andconnected to the first source electrode.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a schematic view showing a liquid crystal display deviceaccording to the related art where a switching element and a drivingcircuit are formed on a single substrate;

FIGS. 2A to 2F are schematic cross-sectional views showing a process offabricating a thin film transistor disposed in a display area of aliquid crystal display device according to the related art;

FIGS. 3A to 3F are schematic cross-sectional views showing a process offabricating n-type and a p-type thin film transistors in a driving areaof a liquid crystal display device according to the related art;

FIG. 4 is a schematic plane view showing an array substrate for a liquidcrystal display device according to an exemplary embodiment of thepresent invention;

FIGS. 5A to 5P are schematic cross-sectional views taken along line“V-V” of FIG. 4 showing a fabricating process of a pixel thin filmtransistor and a storage capacitor in a display area of an arraysubstrate according to an exemplary embodiment of the present invention;

FIGS. 6A to 6P are schematic cross-sectional views taken along line“VI-VI” of FIG. 4 showing a fabricating process of a pixel thin filmtransistor in a display area of an array substrate for a liquid crystaldisplay device according to an exemplary embodiment of the presentinvention;

FIGS. 7A to 7P are schematic cross-sectional views taken along line“VII-VII” of FIG. 4 showing a gate pad in a non-display area of an arraysubstrate according to an exemplary embodiment of the present invention;and

FIGS. 8A to 8P are schematic cross-sectional views showing a fabricatingprocess of n-type and p-type driving thin film transistors in a drivingarea of an array substrate according to an exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, example of which is illustrated in the accompanying drawings.Wherever possible, similar reference numbers will be used throughout thedrawings to refer to the same or like parts.

FIG. 4 is a schematic plane view showing an array substrate for a liquidcrystal display device according to an exemplary embodiment of thepresent invention. FIG. 4 shows a display area and a pad area of thearray substrate, and it does not show a driving area of the arraysubstrate for simplicity.

In FIG. 4, a gate line 112 and a data line 109 are formed on a substrate101 in a display area “DPA.” A gate pad 170 is formed at one end of thegate line 112 and a data pad 175 is formed at one end of the data line109. The gate line 112 intersects the data line 109 to define a pixelregion “P”. A thin film transistor (TFT) “Tr” formed as a switchingelement is connected to the gate line 112 and the data line 109. Thegate pad 170 and the data pad 175 are disposed in a non-display area“NDA” at a periphery of the display area “DPA.” In addition, a commonline 127 is disposed parallel to and spaced apart from the gate line112. A pixel electrode 110 connected to the TFT “Tr” is disposed in thepixel region “P” and overlaps the common line 127 to form a storagecapacitor. The pixel electrode 110 directly contacts the TFT “Tr”without a contact hole.

FIGS. 5A to 5P are schematic cross-sectional views taken along line“V-V” of FIG. 4. FIGS. 6A to 6P are schematic cross-sectional viewstaken along line “VI-VI” of FIG. 4. FIGS. 7A to 7P are schematiccross-sectional views taken along line “VII-VII” of FIG. 4. FIGS. 5A to5P, FIGS. 6A to 6P, and FIGS. 7A to 7P show a fabricating process of apixel thin film transistor, a storage capacitor in a display area, and agate pad disposed in a non-display area of an array substrate accordingto an embodiment of the present invention. In addition, FIGS. 8A to 8Pare schematic cross-sectional views showing a fabricating process ofn-type and p-type driving thin film transistors in a driving area of anarray substrate according to an embodiment of the present invention.

According to the FIGS. 5A, 6A, 7A and 8A, a buffer layer 103 of aninorganic insulating material such as silicon nitride (SiN_(x)) andsilicon oxide (SiO₂) is disposed on a substrate 101 having a drivingarea and a display area. When amorphous silicon is crystallized to apolycrystalline silicon by a laser annealing method, alkali ions such aspotassium ion (K⁺) and sodium ion (Na⁺) may erupt from a substrate dueto a heat produced by a laser beam. The buffer layer 103 preventsdeterioration of polycrystalline silicon due to an alkali ion. Next, atransparent conductive material layer 106 and a metallic material layer107 are sequentially disposed on the buffer layer 103. For example, thetransparent conductive material layer 106 may include one ofindium-tin-oxide (ITO) and indium-zinc-oxide (IZO) whose thickness fitswithin a range of about 500 Å to about 1000 Å. The metallic materiallayer 107 may include molybdenum (Mo) to have a thickness equal to orless than about 3000 Å.

After a first photoresist (PR) layer 108 is disposed on the metallicmaterial layer 107, a gate-pixel mask 170 having a transmissive area“TA,” a blocking area “BA” and a half-transmissive area “HTA” isdisposed over the first PR layer 108. The half-transmissive area “HTA”has a light transmittance lower than the transmissive area “TA” buthigher than the blocking area “BA.” The half-transmissive area “HTA”corresponds to gate electrode areas “GA” of a pixel thin film transistor(TFT) portion “A,” an n-type driving TFT portion “B” and a p-typedriving TFT portion “C.” Furthermore, the half-transmissive area “HTA”corresponds to a pixel electrode area “PA” and a storage capacitor area“StgA” of the pixel TFT portion “A” and a gate pad area “GPA” of thenon-display area. The blocking area “BA” corresponds to a gate line area“GLA.” A positive type PR without exposed portion is used in thisembodiment, however, a negative type PR may be used in anotherembodiment by changing the areas of the gate-pixel mask 170. Then, thefirst PR layer 108 is exposed through the gate-pixel mask 170. Forexample, when the half-transmissive area “HTA” includes a slit, lightmay be irradiated through the slit by diffraction.

In FIGS. 5B, 6B, 7B and 8B, the first PR layer 108 (of FIG. 5A) isdeveloped to form a first gate-pixel PR pattern 108 a and a secondgate-pixel PR pattern 108 b. The first and second gate-pixel PR patterns108 a and 108 b correspond to the half-transmissive area “HTA” and theblocking area “BA” of the gate-pixel mask 170, respectively. As shown inFIG. 6B, the first gate-pixel PR pattern 108 a has a reduced thicknessas compared to the second gate-pixel PR pattern 108 b, and the first andsecond gate-pixel PR patterns 108 a and 108 b are formed through a firstmask process.

In FIGS. 5C, 6C, 7C and 8C, the metallic material layer 107 and thetransparent conductive material layer 106 are sequentially etched usingthe first and second gate-pixel PR patterns 108 a and 108 b as anetching mask to form a transparent conductive material pattern 106 a anda metallic material pattern 107 a.

In FIGS. 5D, 6D, 7D and 8D, after etching the metallic material layer107 and the transparent conductive material layer 106, portions of thefirst and second gate-pixel PR patterns 108 a and 108 b are removed. Forexample, the first and second gate-pixel PR patterns 108 a and 108 b maybe anisotropically removed by a dry etching method such as ashing. Asshown in FIG. 5D, the first gate-pixel PR pattern 108 a (of FIG. 5C) iscompletely removed while a portion of second gate-pixel PR pattern 108 b(of FIG. 6C) having a reduced thickness remains. Then, the metallicmaterial pattern 107 a is etched using the remaining second gate-pixelPR pattern 108 b as an etching mask to expose the transparent conductivematerial pattern 106 a (of FIG. 5C). Accordingly, a pixel electrode 110and a first capacitor electrode 110 a are formed in the pixel TFTportion “A,” and a gate pad 116 is formed in the gate pad area “GPA.” Inaddition, first gate electrode 113 is formed in the gate electrode areas“GA” of the pixel TFT portion “A.” Second gate electrode 114 is formedin the n-type driving TFT portion “B.” Furthermore, third gate electrode115 is formed in the p-type driving TFT portion “C.” As a result, thepixel electrode 110, the first capacitor electrode 110 a, the gate pad116 and the first, second and third gate electrodes 113, 114 and 115include a transparent conductive material.

As shown in FIG. 6D, since the portion of second gate-pixel PR pattern108 b still remains, a gate line 112 including a metallic materialpattern 112 a and a transparent conductive material pattern 112 b areformed in the gate line area “GLA.” Accordingly, resistance increase ofthe gate line 112 is prevented. Furthermore, gate line delay due to suchresistance increase is prevented. In addition, since each of the first,second and third gate electrodes 113, 114 and 115 include a single layerof a transparent conductive material, a size of a step at edge portionsof each of the gate electrodes 113, 114 and 115 becomes small. In asubsequent process, an amorphous silicon layer is disposed on the gateelectrodes 113, 114 and 115, and then the amorphous silicon layer may becrystallized to a polycrystalline silicon layer through a laserannealing method. As compared to the smaller step at edge portions ofeach of the gate electrodes 113, 114 and 115, when edge portions includeincreased step size, such increased size step may cause deterioration ofthe polycrystalline silicon layer during the crystallization process.However, in an embodiment, the size of the step for each of the gateelectrodes 113, 114 and 115 are formed small enough to prevent thedeterioration of the polycrystalline silicon layer.

In FIGS. 5E, 6E, 7E and 8E, after the first and second gate-pixel PRpatterns 108 a and 108 b are removed, a gate insulating layer 118 isdisposed on the gate line 112, the first, second and third gateelectrodes 113, 114 and 115, and the gate pad 116. The gate insulatinglayer 118 may include one of inorganic insulating materials such assilicon nitride (SiN_(x)) and silicon oxide (SiO₂). Thereafter, anamorphous silicon layer is disposed on an entire surface of the gateinsulating layer 118. The amorphous silicon layer is crystallized to apolycrystalline silicon layer 123 by irradiating a laser beam. Theamorphous silicon layer may be crystallized through an excimer laserannealing (ELA) method or a sequential lateral solidification (SLS)method using an excimer laser having one of wavelengths 193 nm (ArF),248 nm (KrF), 308 nm (XeCl), and 351 nm (XeF). Since each of the first,second and third gate electrodes 113, 114 and 115 are formed of a singlelayer of a transparent conductive material, the step size formed at eachof the gate electrodes 113, 114 and 115 on the substrate 101 is reduced.Accordingly, deterioration of the polycrystalline silicon layer duringthe crystallization process through ELA method or SLS method isprevented and crystallinity of the polycrystalline silicon layer isimproved.

In FIGS. 5F, 6F, 7F and 8F, first and second p+ PR patterns 131 and 130are disposed on the polycrystalline silicon layer 123 through a secondmask process. The first p+ PR pattern 131 covers a first portion 126 bof the polycrystalline silicon layer 123 corresponding to the gateelectrode 115 in the p-type driving TFT portion “C”. Second portion 126a of the polycrystalline silicon layer 123 at both sides of the firstportion 126 b in the p-type driving TFT portion “C” is exposed. Inaddition, the second p+ PR pattern 130 covers the entire polycrystallinesilicon layer 123 in the pixel TFT portion “A,” the gate line area“GLA,” the gate pad area “GPA”, and the n-type driving TFT portion “B.”

Next, the polycrystalline silicon layer 123 is doped with highconcentration p-type impurities (p+) using the first and second p+ PRpatterns 131 and 130 as doping masks. For example, the concentration ofthe p-type impurities may be within a range of about 1×10¹⁵ cm⁻² toabout 9×10¹⁶ cm⁻². Accordingly, as shown in FIG. 8F, the second portion126 a of the polycrystalline silicon layer 123 in the p-type driving TFTportion “C” is doped with the high concentration p-type impurities (p+)to function as a p-type ohmic contact region, while the first portion126 b is not doped with the high concentration p-type impurities (p+).The first portion 126 b functions as an intrinsic silicon layer.Similarly, the polycrystalline silicon layer 123 in the pixel TFTportion “A” of FIG. 5F, the n-type driving TFT portion “B” of FIG. 8F,and the gate pad area “GPA” of FIG. 7F, is not doped with the highconcentration p-type impurities (p+) to remain as an intrinsic layer.After doping with the high concentration p-type impurities (p+), thefirst and second p+ PR patterns 131 and 130 are removed by a dry etchingmethod such as ashing or a wet etching method such as stripping.

In FIGS. 5G, 6G, 7G and 8G, first and second n+ PR patterns 135 and 136are disposed on the polycrystalline silicon layer 123 through a thirdmask process. As shown in FIG. 5G and FIG. 8G, first portions 124 a and125 a of the polycrystalline silicon layer 123 in the pixel TFT portion“A” (of FIG. 5G) and the n-type driving TFT portion “B” (of FIG. 8G) areexposed through the first and second n+ PR patterns 135 and 136. Inaddition, the first n+ PR pattern 135 covers second and third portions124 b, 124 c, 125 b and 125 c in the pixel TFT portion “A” and then-type driving TFT portion “B.” The third portions 124 c and 125 ccorrespond to the first gate electrode 113 in the pixel TFT portion “A”and the second gate electrode 114 in the n-type driving TFT portion “B,”respectively. Furthermore, the second portions 124 b formed between thefirst portion 124 a and the third portion 124 c of FIG. 5G have a widthmatched to a lightly doped drain (LDD) length. Similarly, the 2ndportions 125 b formed between the first portion 125 a and the thirdportion 125 c of FIG. 8G have a width matched to a lightly doped drain(LDD) length.

As shown in FIG. 5G, a portion of the polycrystalline silicon layer 123in the pixel electrode area “PA” is covered with the second n+ PRpattern 135, while a portion of storage capacitor area “StgA” isexposed. In addition, the second n+ PR pattern 136 covers the entirepolycrystalline silicon layer 123 in the gate line area “GLA” of FIG.6G, the gate pad area “GPA” of FIG. 7G, and the n-type driving TFTportion “B” of FIG. 8G.

Next, the polycrystalline silicon layer 123 is doped with highconcentration n-type impurities (n+) using the first and second n+ PRpatterns 135 and 136 as doping masks. For example, the concentration ofthe n-type impurities may be within a range of about 1×10¹⁵ cm⁻² toabout 9×10¹⁶ cm⁻². Accordingly, the first portions 124 a and 125 a inthe pixel TFT portion “A” and the n-type driving TFT portion “B” aredoped with the high concentration n-type impurities (n+) to function asa n-type ohmic contact region, while the second and third portions 124b, 124 c, 125 b and 125 c are not doped with the high concentrationn-type impurities (n+) to remain as an intrinsic silicon layer.Similarly, the polycrystalline silicon layer 123 in the storagecapacitor area “StgA” is doped with the high concentration n-typeimpurities (n+) to be a second capacitor electrode 127 of n+ dopedpolycrystalline silicon.

In FIGS. 5H, 6H, 7H and 8H, after doping with the high concentrationn-type impurities (n+), portions of the first and second n+ PR patterns135 and 136 are removed. For example, the first and second n+ PRpatterns 135 and 136 may be isotropically removed by a dry etchingmethod such as ashing or a wet etching method such as stripping.Accordingly, a side portion and a top portion of the first and second n+PR patterns 135 and 136 may be equally removed. As a result, as shown inFIG. 5H and FIG. 8H, the second portions 124 b and 125 b in the pixelTFT portion “A”, the n-type driving TFT portion “B” and a side portion128 in the pixel electrode area “PA” are exposed, and a thickness of thefirst and second n+ PR patterns 135 and 136 is reduced.

Next, the polycrystalline silicon layer 123 is doped with lowconcentration n-type impurities (n−) using the reduced first and secondn+ PR patterns 135 and 136 as doping masks. For example, theconcentration of the n-type impurities may be within a range of about1×10¹³ cm⁻² to about 9×10¹³ cm⁻². Accordingly, as shown in FIG. 5H, thefirst portion 124 a and the second portion 124 b in the polycrystallinesilicon layer 123, a side portion 128 in the pixel electrode area “PA”,and the second capacitor electrode 127 in the storage capacitor area“StgA” in the pixel TFT portion “A” are doped with the low concentrationn-type impurities (n−). Similarly, as shown in FIG. 8H, the firstportion 125 a and the second portion 125 b in the polycrystallinesilicon layer 123, and the side portion 128 in the n-type driving TFTportion “B” are doped with the low concentration n-type impurities (n−).After doping with the low concentration n-type impurities (n−), thefirst and second n+ PR patterns 135 and 136 having the reduced thicknessare removed by a dry etching method such as ashing or a wet etchingmethod such as stripping.

Since the first portions 124 a and 125 a of the polycrystalline siliconlayer 123 in the pixel TFT portion “A”, the n-type driving TFT portion“B”, and the second capacitor electrode 127 in the storage capacitorarea “StgA” are already doped with the high concentration n-typeimpurities (n+), the impurity concentration thereof is not affected bythe low concentration n-type impurities (n−) doping and remains as ahigh concentration. In addition, the side portion 128 in the pixelelectrode area “PA” is removed in a subsequent process. As a result, thesecond portions 124 b and 125 b in the pixel TFT portion “A” and then-type driving TFT portion “B” are doped with the low concentrationn-type impurities (n−) to be LDD regions. The LDD regions distribute astrong electric field to a weak electric field, thereby hot carriers arereduced and leakage current is prevented. Accordingly, the LDD regionsare formed in an n-type TFT and disposed between an ohmic contact regionof n+ impurity-doped silicon and an active region of intrinsic silicon.

Through a plurality of doping processes including the p+ impurities, then+ impurities and the n− impurities, n-type TFTs in the pixel TFTportion “A” of FIG. 5I, the n-type driving TFT portion “B” and a p-typeTFT in the p-type driving TFT portion “C” of FIG. 8I, are obtained. Asshown in FIG. 5I, a first semiconductor layer 124 in the pixel TFTportion “A” includes the active region 124 c of intrinsic siliconoverlapping the first gate electrode 113, the LDD regions 124 b of n−impurity-doped silicon at both sides of the active region 124 c, and theohmic contact regions 124 a of n+ impurity-doped silicon at one side ofthe LDD regions 124 b. Similarly, as shown in FIG. 8I, a secondsemiconductor layer 125 in the n-type driving TFT portion “B” includesthe active region 125 c of intrinsic silicon overlapping the gateelectrode 114, the LDD regions 125 b of n− impurity-doped silicon at oneside of the active region 125 c and the ohmic contact regions 125 a ofn+ impurity-doped silicon at one side of the LDD regions 125 b. A thirdsemiconductor layer 126 in the p-type driving TFT portion “C” of FIG.8I, includes the active region 126 b of intrinsic silicon overlappingthe gate electrode 115, and the ohmic contact regions 126 a of p+impurity-doped silicon at both sides of the active region 126 b. Inaddition, a fourth semiconductor layer 127 in the storage capacitor area“StgA” of n+ impurity-doped silicon forms a second electrode of astorage capacitor because of its conductive property. A dummy intrinsicportion 123 a and a dummy doped portion 128 of the polycrystallinesilicon layer are removed in a subsequent process. In an embodiment, thepolycrystalline silicon layer is doped with n-type impurities afterdoping with p-type impurities. However, the polycrystalline siliconlayer may be doped with n-type impurities first, then doped with p-typeimpurities in another embodiment.

In FIGS. 5I, 6I, 7I and 8I, a passivation layer 150 is disposed on thefirst, second, third and fourth semiconductor layers 124, 125, 126 and127, the dummy intrinsic portion 123 a and the dummy doped portion 128of the polycrystalline silicon layer. The passivation layer 150 mayinclude one of inorganic insulating materials such as silicon nitride(SiN_(x)) and silicon oxide (SiO₂). In an embodiment, the passivationlayer 150 includes a single layer, however, the passivation layer 150may include a multiple layer of different insulating materials inanother embodiment.

In FIGS. 5J, 6J, 7J and 8J, a second PR layer 183 is disposed on thepassivation layer 150 and an active-contact mask 190 having atransmissive area “TA,” a half-transmissive area “HTA” and a blockingarea “BA” is disposed over the second PR layer 183. Thehalf-transmissive area “HTA” has a light transmittance lower than thetransmissive area “TA” and higher than the blocking area “BA.” Theblocking area “BA” of a positive type PR corresponds to the activeregion 124C and the storage capacitor area “StgA” in the pixel TFTportion “A”. Similarly, the blocking area “BA” of the positive type PRcorresponds to the active region 125C in the n-type driving TFT portion“B” and the active region 126C in the p-type driving TFT portion “C”. Inaddition, the half-transmissive area “HTA” corresponds to side portionsof the ohmic contact regions 124 a of FIG. 5J, 125 a and 126 a of FIG.8J, and the gate line area “GLA” of FIG. 6J. The other regions of thesubstrate 101 correspond to the transmissive area “TA.” Then, the secondPR layer 183 is exposed through the active-contact mask 190. Forexample, when the half-transmissive area “HTA” includes a slit, lightmay be irradiated through the slit by diffraction.

In FIGS. 5K, 6K, 7K and 8K, the second PR layer 183 (of FIG. 5J) isdeveloped to form a first active-contact PR pattern 183 a and a secondactive-contact PR pattern 183 b. The first active-contact PR pattern 183a corresponds to the blocking area “BA”, and the 2nd active-contract PRpattern 183 b corresponds to the half-transmissive area “HTA” of theactive-contact mask 190. Accordingly, the first active-contact PRpattern 183 a has a thickness greater than the second active-contact PRpattern 183 b. As a result, the first and second active-contact PRpatterns 183 a and 183 b are formed on the passivation layer 150 and thetransmissive area “TA” of the active-contact mask 190 exposes the otherportions of the passivation layer 150 through a fourth mask process.

In FIGS. 5L, 6L, 7L and 8L, the passivation layer 150 (of FIG. 5K), thesemiconductor layer of polycrystalline silicon layer 123, and the gateinsulating layer 118 are sequentially etched using the first and secondactive-contact PR patterns 183 a and 183 b as an etching mask.Accordingly, as shown in FIG. 5L, the first semiconductor layer 124including the ohmic contact region 124 a, the LDD region 124 b and theactive region 124 c are defined in the pixel TFT portion “A” to form anisland shape. Similarly, as shown in FIG. 8L, the second and thirdsemiconductor layers 125 and 126 having an island shape are defined inthe n-type driving TFT portion “B” and the p-type driving TFT portion“C,” respectively. The second semiconductor layer 125 includes the ohmiccontact region 125 a, the LDD region 125 b, and the active region 125 c.The third semiconductor layer 126 includes the ohmic contact region 126a and the active region 126 b. In addition, as shown in FIG. 5L, thefourth semiconductor layer 127 having an island shape is defined in thestorage capacitor area “StgA” and the pixel electrode 110 in the pixelelectrode area “PA” is exposed. The portion of the passivation layer 150(of FIG. 5K) are etched to form a first passivation pattern 150 a underthe first and second active-contact PR patterns 183 a and 183 b.

In FIGS. 5M, 6M, 7M and 8M, after etching the passivation layer 150 (ofFIG. 5K), the semiconductor layer of polycrystalline silicon layer 123,the gate insulating layer 118, the second active-contact PR pattern 183b, and portions of the first active-contact PR patter 183 a are removed.For example, the first and second active-contact PR patterns 183 a and183 b may be anisotropically removed by a dry etching method such asashing. Accordingly, the first active-contact PR pattern 183 a remainswith a reduced thickness, while the second active-contact PR pattern 183b is completely removed. As a result, a portion of the first passivationpattern 150 a corresponding to the second active-contact PR pattern 183b is exposed.

In FIGS. 5N, 6N, 7N and 8N, the exposed portions of the firstpassivation pattern 150 a are etched using the remaining firstactive-contact PR pattern 183 a as an etching mask to define a secondpassivation pattern 150 b covering portions of the active regions 124 cof FIG. 5N, 125 c and 126 b of FIG. 8N, and exposing portions of theohmic contact regions 124 a, 125 a and 126 a. After etching the portionof the first passivation pattern 150 a, the remaining firstactive-contact PR pattern 183 a is removed by a dry etching method suchas ashing or a wet etching method such as stripping.

In FIGS. 5O, 6O, 7O and 8O, first source and drain electrodes 160 a and160 b in the pixel TFT portion “A”, second source and drain electrodes161 a and 161 b in the n-type driving portion “B”, and third source anddrain electrodes 162 a and 162 b in the p-type driving TFT are formed onthe second passivation pattern 150 b through a fifth mask process. Atthe same time, a data line (not shown) is formed on the buffer layer103. The first source and drain electrodes 160 a and 160 b, the secondsource and drain electrodes 161 a and 161 b, the third source and drainelectrodes 162 a and 162 b, and the data line may include one ofmolybdenum (Mo), chromium (Cr), aluminum (Al), copper (Cu), and alloythereof. As shown in FIG. 5D, the first source and drain electrodes 160a and 160 b are formed spaced apart from each other having the firstgate electrode 113 defining the center portion and connected to theohmic contact region 124 a in the pixel TFT portion “A.” Similarly, asshown in FIG. 8O, the second source and drain electrodes 161 a and 161 bare formed spaced apart from each other having the second gate electrode114 defining the center portion and connected to the ohmic contactregion 125 a in the n-type driving TFT portion “B” In addition, thethird source and drain electrodes 162 a and 162 b are formed spacedapart from each other having the third gate electrode 115 deleting thecenter portion and connected to the ohmic contact region 126 a in thep-type driving TFT portion “C.”

Since the second passivation pattern 150 b covers the active regions 124c, 125 c and 126 b of the polycrystalline silicon layer 123, the activeregions 124 c, 125 c and 126 b forming a channel region are notdeteriorated during etching process. The first to third source and drainelectrodes 160 a, 160 b, 161 a, 161 b, 162 a and 162 b and the data lineare formed during the etching process. In addition, the first sourceelectrode 160 a is connected to the data line and the first drainelectrode 160 b contacts a portion of the pixel electrode 110 in thepixel TFT portion “A”. The other portion of the pixel electrode 110 inthe pixel electrode area “PA” is exposed. Furthermore, the gate pad 116in the gate pad area “GPA” of FIG. 7O, the dummy intrinsic portion 123 ain the gate electrode area “GA” and the gate line area “GLA” of FIG. 6Oand the first passivation pattern 150 a in the storage capacitor area“StgA” of FIG. 5O are exposed.

In FIGS. 6P, 7P and 8P, the exposed dummy intrinsic portion 123 a of thepolycrystalline silicon layer 123 in the gate electrode area “GA” andthe gate line area “GLA” is removed using the first to third source anddrain electrodes 160 a, 160 b, 161 a, 161 b, 162 a and 162 b and thedata line as an etching mask. For example, the exposed dummy intrinsicportion 123 a may be etched through a dry etching method. In anotherembodiment, the dummy intrinsic portion 123 a in the gate electrode area“GA” and the gate line area “GLA” may be removed during an etching stepof the passivation layer 150 (of FIG. 5K), the semiconductor layer ofpolycrystalline silicon, and the gate insulating layer 118 shown in FIG.6L, thereby this etching step of the exposed dummy intrinsic portion 123a may be omitted.

In this embodiment of FIGS. 5A to 8P, an n-type driving TFT and a p-typedriving TFT are formed using a CMOS logic in a driving area and an arraysubstrate for an LCD device to drive a circuit. In an embodiment, afive-mask process is implemented to fabricate the n-type and the p-typedriving TFTs. In another embodiment, a driving circuit maybe formedusing either an NMOS logic or a PMOS logic. In such embodiment, thedriving circuit may include only one of an n-type driving TFT and ap-type driving TFT. Accordingly, a mask process for one of p+ dopingstep and n+ doping step may be omitted, and an array substrate for anLCD device including a driving circuit may be fabricated through afour-mask process.

In the present invention, polycrystalline silicon TFTs of an LCD deviceincludes a bottom gate structure. A gate line and a pixel electrode fora polycrystalline silicon TFT are formed through one-mask process usinga mask having a half-transmissive area. In addition, a passivationlayer, a polycrystalline silicon layer, and a gate insulating layer fora polycrystalline silicon TFT are also formed through one-mask processusing same half transmissive area mask. Accordingly, an array substratefor an LCD device including a driving circuit is fabricated through afive-mask process. As a result, production time and production cost arereduced, and higher production yield are achieved. Moreover, since apassivation pattern of an island shape is formed on a polycrystallinesilicon layer having an active region and an ohmic contact region,damages to a channel region of a polycrystalline silicon TFT during anetching process are prevented. Furthermore, when a driving circuit isformed to be driven by one of a PMOS logic and an NMOS logic, an arraysubstrate for an LCD device including a driving circuit is fabricatedthrough a four-mask process. Accordingly, production time, productioncost and production yield are further improved. Additionally, since agate electrode includes a thin single layer of a transparent conductivematerial, deterioration due to an increased step size of a gateelectrode is prevented and crystallinity of a polycrystalline siliconlayer is improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. An array substrate structure for a liquid crystal display device,comprising: first, second and third gate electrodes on a substratehaving a display area and a non-display area, the display area having apixel TFT portion and a pixel electrode area, and the non-display areahaving an n-type driving TFT portion and a p-type driving TFT portion,the first gate electrode disposed in the pixel TFT portion, the secondgate electrode disposed in the n-type driving TFT portion, the thirdgate electrode disposed in the p-type driving TFT portion; a gate linein the display area on the substrate; a pixel electrode in the pixelelectrode area on the substrate; a gate insulating layer on the first,second, and third gate electrodes, the gate line, and the pixelelectrode; first, second and third semiconductor layers ofpolycrystalline silicon on the gate insulating layer, the firstsemiconductor layer disposed in the pixel TFT portion, the secondsemiconductor layer disposed in the n-type driving TFT portion, and thethird semiconductor layer disposed in the p-type driving TFT portion; apassivation pattern on the first, second and third semiconductor layers,the passivation pattern exposing side portions of each of the first,second and third semiconductor layers; first source and drainelectrodes, second source and drain electrodes, and third source anddrain electrodes on the substrate, the first source and drain electrodescontacting the side portions of the first semiconductor layer, thesecond source and drain electrodes contacting the side portions of thesecond semiconductor layer, the third source and drain electrodescontacting the side portions of the third semiconductor layer; and adata line crossing the gate line and connected to the first sourceelectrode.
 2. The substrate structure according to claim 1, wherein thefirst, second and third gate electrodes and the pixel electrode includea single layer of a transparent conductive material.
 3. The substratestructure according to claim 1, wherein the gate line includes a doublelayer of a transparent conductive material and a metallic material. 4.The substrate structure according to claim 1, further comprising a firstcapacitor electrode connected to the pixel electrode and a secondcapacitor electrode over the first capacitor electrode.
 5. The substratestructure according to claim 4, wherein the first capacitor electrodeincludes a transparent conductive material, and wherein the secondcapacitor electrode includes the polycrystalline silicon material. 6.The substrate structure according to claim 1, wherein the first drainelectrode directly contacts the pixel electrode.
 7. The substratestructure according to claim 1, wherein the gate insulating layer andthe passivation pattern have an island shape.